K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2018-11-27T19:50:58.111150Z
K 7
svn:log
V 291
Improve sigonstack().

Avoid relying on unsigned overflow for the test.
Simplify expressions to avoid duplicate check for the range.
Style.
Add herald comment.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D18361

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